The currently produced devices either include resilient seals which are pressed between the corresponding portions of housing halves, or need very close adjustment workings for obtaining a satisfactory air-tightness.
The housings for the above-mentioned application, as well as many other housings for containing various parts are more often made of molded synthetic material, and it often happens that the corresponding portions of housing halves exhibit important dimension differences.
This is especially the case for rectilinear connecting portions, which often tend to form a bend with more or less deflection, so that it becomes necessary in practice to provide securing clips or to carry out relatively complex clamping.